1. Field of the Invention
This invention relates to a system for manufacturing optical disks, and more particularly, to a system and a method for mounting a hub to a data recording optical disk used as a recording medium for an information processing system, such as a computer.
2. Description of the Related Art
Data recording optical disks have much higher information recording density than optical audio disks used as a recording medium for a sound reproduction system. Accordingly, the data recording optical disks must be accurately mounted to the spindle of a disk drive unit, and to this end, a hub is attached at the center of the optical disks and a spindle hole is bored at the center of the hub with high precision.
When mounting the hub to an optical disk, the center of a hub mounting hole of the optical disk must be aligned with the axis of the spindle hole of the hub with high precision. Therefore, conventionally, apparatuses for mounting a hub to an optical disk are provided with a so-called X-Y stage movable in directions perpendicular to each other, and a disk mount is arranged on the X-Y stage. The disk mount has a mount surface facing upward, on which an optical disk is placed, and a mandrel projects from the central portion of the mount surface, to be fitted through the hub mounting hole of the optical disk. Accordingly, when an optical disk is placed on the disk mount with the mandrel fitted through the hub mounting hole of the optical disk, the center of the optical disk is automatically aligned with the axis of the mandrel.
Above the disk mount, moreover, a liftable loading rod is arranged. The loading rod extends vertically and has a chuck at a lower end thereof for accurately positioning the hub and holding the same. Namely, when the hub is held by the chuck, the axis of the spindle hole of the hub and the axis of the loading rod are automatically aligned with each other.
According to the above-described conventional apparatus, the position of the disk mount is adjusted by operating the X-Y stage such that the axis of the mandrel coincides with that of the loading rod, whereby the axis of the mandrel is brought into alignment with the axis of the loading rod, i.e., the origin. Therefore, after carrying out such position adjustment, if a hub is clamped by the chuck of the loading rod and the loading rod is lowered toward an optical disk which has been placed on the mount surface of the disk mount with the aid of the mandrel, the hub can be automatically fitted in the hub mounting hole of the optical disk, with the axis of the spindle hole thereof aligned with the center of the optical disk.
In the aforesaid X-Y stage, however, the axis of the disk mount is occasionally deviated from the axis of the loading rod, namely, from the origin, due to thermal influences such as an increase in ambient temperature or heat produced in the apparatus. Therefore, to ensure high-precision mounting of a hub to an optical disk by using the above-described apparatus, alignment of the axis of the disk mount with the origin, namely, origin adjustment, must be regularly carried out. For example, the alignment may be carried out each time a predetermined number of optical disks have been subjected to the hub mounting process, or at predetermined intervals of time, but this alignment requires much time and thus lowers the rate of operation of the apparatus.
To improve the productivity of optical disks with a hub, on the other hand, not only the time required for the above-described hub mounting process but also the time required for securely fixing the hub to the optical disk after the hub mounting process must be shortened. To this end, an ultraviolet-curing adhesive is used for fixing the hub to the optical disk. More specifically, before actually fitting the hub in the hub mounting hole of the optical disk, an ultraviolet-curing adhesive is applied to a surface of the optical disk to which the hub is to be bonded, i.e., a region of the disk around the hub mounting hole. Simultaneously with the mounting of the hub to the hub mounting hole of the optical disk, the ultraviolet-curing adhesive is irradiated with an ultraviolet radiation through the hub and is cured, whereby the hub can be instantly secured to the optical disk.
Since the ultraviolet radiation is radiated to the adhesive through the hub, as mentioned above, the hub must be made of a material capable of transmitting the ultraviolet radiation therethrough, i.e., a transparent synthetic resin which is also used for the optical disk. On the other hand, to allow high-precision machining of the spindle hole, the spindle hole need be bored through a thin circular plate made of a metal. For this reason, the hub is composed of a transparent body of synthetic resin, and a metal plate having a spindle hole bored therethrough and attached to the body. Hubs of this type are, however, disadvantageous in respect of the number of parts, requiring much labor and cost to manufacture the hubs.
A first object of this invention is to provide a system and a method which permit high-precision mounting of a hub to an optical disk and which can improve the productivity of optical disks with a hub, and a second object of the invention is to provide a system which permits a hub, made solely of a metallic material, to be bonded to an optical disk by using an ultraviolet-curing adhesive.